1. Field of the Invention
This invention relates to novel skin-marking compositions, to their use to render skin fluorescent under ultraviolet light and to marking devices comprising them.
2. Description of the Related Art
The use of skin-marking compositions to delineate boundaries of bodily areas requiring medical therapy, such as for radiation treatment of cancer, to identify areas contacted with allergens, to monitor the status of ring worm and other skin infections, and for other dermatological purposes, is conventional. Typically, visible compounds, such as bright purple or green dyes or inks, have been used. See, for example, U.S. Pat. No. 3,551,554. Although adequate for marking purposes, a visible dye has an adverse psychological impact on a patient so marked, because of the dye's conspicuous visibility during a typically prolonged course of radiation or other therapy.
To avoid this problem, U.S. Pat. No. 3,640,889 utilizes skin-marking compositions that contain a fluorescent dyestuff which becomes visible only under ultraviolet light. Thus, at the times prescribed for treatment, the site so marked can be perceived by the therapist upon illumination of the marked area with ultraviolet light.
To render its marking composition more permanent, the '889 patent incorporates a polyvinyl acetate compound into its marking composition to provide a coating layer on the surface of the skin to entrap dye molecules and render the composition resistant to washing and normal abrasion, thereby extending the time period during which the dye remains on the skin and can be observed. However, such a vinyl layer is physically uncomfortable for a patient so treated. The coating may also inhibit the normal sloughing of surface skin layers, as well as the perspiratory and other natural functions of the skin. Moreover, the compositions can still be removed by washing, thereby necessitating repeated applications of dye during the course of therapy. Such reapplication is disadvantageous in that it inefficiently consumes the valuable time of medical professionals and introduces the opportunity for inaccurately or erroneously remarking therapy area boundaries.
The use of fluorescent dyestuffs to temporarily mark skin is well known; for example, in allergy diagnosis to delineate areas of the skin to which various allergens are applied and to identify customers who have paid admission in amusement areas. Such dyestuffs are readily removed by washing.
Florescamine (4-phenylspiro[furan-2(3H),1'-phthalan]-3,3'-dione) and other structurally related furanones are reagents which, although not fluorescent themselves, are known to react with primary and secondary amines to form a reaction product which is intensely fluorescent under ultraviolet light. They are known as fluorogenic dyes because they become fluorescent only after undergoing a chemical reaction with amino acids. These reagents are used as a rapid and sensitive in vitro assay of amino acids, peptides, proteins and other primary and secondary amines. Such dyes are useful as quantitative, fluorometric indicators because their substrate proteins are present in solution and are readily accessible on all sides. See U.S. Pat. Nos. 3,812,181; 3,830,629; 3,871,825; 3,969,373; 4,045,487; and 4,238,589; which disclosures are incorporated herein by reference. Although the latter patents disclose the furanones as fluorogenic assay reagents for primary and secondary amine-containing compounds generally, including living organisms such as bacteria and tapeworms, the patents make no reference to tissues such as skin.
Moreover, one would not expect that they would similarly react with the relatively inaccessible and non-reactive proteins of the skin, because of the barrier layers that affect dye molecules, such as the various protective processes inherent to the skin that resist penetration and absorption of foreign substances. The structure of proteins is a significant factor also. Binding of dye molecules is dependent upon protein geometry and size, and the accessibility of a protein to the dye. Therefore, protein cell surface receptors that are exposed to the surrounding fluid medium of in vitro cell cultures, or the binding proteins that are present upon the external surfaces of cestodes to attach to and ingest dissolved particulate matter, all behave quite differently from the cuticle, the outer horny layer of skin, that functions to resist penetration by foreign substances. This is confirmed by the fact that if skin is contacted with a solution of one of these furanone compounds, there is virtually no evidence of such a fluorescent reaction product being produced for a substantial period of time. Furthermore, even if exposed surface proteins on the skin did bind some molecules of the dye, this would be inadequate for marking purposes because the outermost skin layers are continually lost by washing or abrasion.
Surprising, we have found that if skin is contacted with one of the aforesaid furanones, after about 15 to 30 minutes, a reaction product with the skin is produced which is invisible under ordinary light but which intensely fluoresces under ultraviolet light. Even more surprising, this reaction product is very permanent and resists removal by bathing or showering for the two or three week normal lifetime of epidermis.
Marking compositions that are only visible under ultraviolet light are also useful as a means of identifying those persons who have come into contact with inanimate objects (such as trucks or boats), or living matter (such as shrubs) or substances (such as hazardous wastes or chemical products) which have previously been coated or treated with these compositions. Military and civilian applications of a fluorescent dye for this purpose are discussed in U.S. Pat. No. 4,219,438. However, this reference teaches the necessary concurrent use of a fluorescent dye along with several solvent and resin components to enhance the useful lifetime of the marker. The fluorogenic reagents of the present invention, when used for marking purposes, are advantageous because they do not require a multi-component mixture, and they are effective when painted or sprayed on an object and then allowed to dry. Furthermore, the fluorogenic compositions are effective at significantly lower concentrations than the prior art dyes which do not selectively bond to epidermal proteins. Most important, because they must bind to protein in order to become fluorescent, in most instances their presence cannot be detected by examination of the object coated with, or material containing, these reagents under an ultraviolet lamp.
It is an object of this invention to provide novel skin-marking compositions that react with the skin to form long-lived reaction products that are invisible under ordinary light but are visible under ultraviolet light. It is another object to provide novel applicators and methods for marking skin to render it fluorescent to ultraviolet light. A further object is to provide a novel method for marking inanimate objects so as to permit identification of persons who come into contact with them. Other objects will be apparent to those skilled in the art.